docs: def import_preferred_memcache_lib(self, servers):
          """Returns an initialized memcache client.  Used by the constructor."""
          try:
              import pylibmc
          except ImportError:
              pass
          else:
              return pylibmc.Client(servers)
  
          try:
              from google.appengine.api import memcache
          except ImportError:
              pass
          else:
              return memcache.Client()
  
          try:
              import memcache
          except ImportError:
              pass
          else:
              return memcache.Client(servers)